There have been known conventional refrigeration devices for containers (see for example Patent Literature 1). When a cargo such as fruits is transported in such a container, quarantine restrictions (for example those by U.S. Department of Agriculture (USDA) or those by Perishable Products Export Control Board (PPECB, export certification agency commissioned by South African Department of Agriculture, Forestry and Fisheries) for pest control are imposed and low-temperature treatment is carried out accordingly so that the temperature of the fruits satisfies a predetermined low temperature condition for a predetermined period in order to prevent pests such as subterranean fruit flies from coming into importing countries together with the transported fruits.
Therefore, if the temperature of fruits in transit does not satisfy the low temperature condition for the predetermined period, the low-temperature treatment is determined to be invalid and the fruits would be denied entry. More specifically, in the low-temperature treatment of fruits, the temperature of the fruits must surely satisfy the low temperature condition for the period determined by the quarantine regulations.
Therefore, the user of the container must carry out cumbersome works of periodically or continuously monitoring the temperature of the interior and the temperature of the cargo and of manually adjusting the set temperature of the refrigeration device from time to time so that the low-temperature treatment is normally carried out.
For example, during the periodic or continuous monitoring, the user must manually change the setting to lower or raise the set temperature of the refrigeration device when the temperature of the cargo tends to approach the upper or lower limit value in the low temperature condition. More specifically, in the conventional refrigeration device, the refrigerant circuit is automatically controlled so that the blow-out temperature approaches the set temperature and the interior is refrigerated, while the automatic control does not take into account fluctuations in the temperature of the cargo, the user must carry out the cumbersome works of periodically or continuously monitoring the temperature of the cargo and manually adjust the set temperature for the blow-out temperature from time to time so that the low-temperature treatment is normally carried out.